Conventionally, thin film solar cells had problems in power generating efficiency, durability and cost. In addition, in case where a solar cell is installed on a building, generally, panel shaped solar cell units (including back side insulation material, a negative electrode, a power generation element, a transparent electrode and a surface protection layer) had been attached to an exterior section, such as a roof, with a stand set later on. In order to make the attachment of the solar cell with such a stand set unnecessary, various sorts of configurations in which a solar cell has been integrated onto a roof material with adhesives have been proposed.
For example, in Japanese Patent Application Publication No. H11-166304, (a patent document No. 1), a solar cell in which a steel plate configuring the roofing material and a solar cell have been integrated is described. The described roofing material is formed by a solar cell having a protective layers, such as a fluorine-resin film, an anti-reflection film for the sunlight to be easily absorbed and a PN-junction type multi-layer structure that is configured with silicon or an amorphous silicon, an adhesive layer for attaching the solar cell onto the steel plate, a coating film for ensuring insulation when attaching the solar cell to the steel plate and a coating film for protecting and insulating the steel plate.
Japanese Patent Application Publication No. 2000-145074 (patent document No. 2) discloses a roof material in which a solar cell module having flexibility of being formed into a sheet-shape is integrated with a surface of a ceramic roof base material having a curved surface, for example, a calcinated tile that is composed of hydraulic property raw materials, such as cement and gypsum, and of inorganic materials by adhering with adhesives.
Further, Japanese Patent Application Publication No. 2002-4529 (patent document No. 30) discloses a solar cell module integrated to building-materials wherein the back surface of a solar cell panel is fixed onto a building-material panel with adhesives excluding end rim sections of both the back surface of the solar cell panel and the building-material panel.
Furthermore, Japanese Patent Application Publication No. 2002-151718 (patent document 4) discloses an example where a thin film solar cell is attached onto a negative electrode structured by silver or aluminum on a polyimide film attached onto a aluminum composite plate as a back sealing layer. In this case, there is no description of directly using aluminum of the aluminum composite board as a negative electrode. In addition, the fluorine resin film is used for the surface protective layer.
Furthermore, Japanese Patent Application Publication No. 2001-267616 (patent document 5) discloses a method of forming a solar cell integrated by utilizing a plating steel plate and a painted steel plate as a substrate, utilizing polyester resin or fluorine resin on the back side surface of the negative electrode, namely, on the surface of the steel plate as an insulation material and laminating the whole section with the fluorine resin film. Also in this example, a plating steel plate and a painted steel plate are not directly used as the negative electrode. Further, the fluorine resin film is used on the surface of the protective layer.